The present invention relates to data processing in distributed systems and more specifically, to processing data in a distributed database system (also called a federated database or federated database system) which manages data stored in database(s) and at least one complete or partial copy of the data.
Heterogeneous, distributed data is commonly stored and analyzed in federated database systems. A federated database system is a type of distributed data processing system, also referred to as “meta-database management system,” which transparently maps multiple autonomous database systems into a single “federated database.” The constituent databases of the federated database are interconnected via a computer network and may be geographically decentralized. Because the constituent database systems remain autonomous, a federated database system is an alternative to the task of merging several disparate databases. A federated database is a composite of all constituent databases in a federated database system, whereby each constituent database system maintains its respective interface for receiving database queries. Each constituent database system stores and autonomously maintains a catalog descriptive of the tables of the respective constituent database. Typically, there is no unified, central schema that encompasses all of the information available from the members (that is, constituent databases) of the federation (that is, the federated database considered as a whole).
In case it should be necessary to integrate and synchronize at least parts of the data stored in different constituent database management systems of a federated database system, additional protocols are typically implemented for synchronizing the data, for example for example “two-phase commit protocols (2PC)” or “three-phase commit protocols (3PC).”